Hybrid dysgenesis is a syndrome of associated aberrant traits in drosophila melanogaster which occurs non-reciprocally in the F1 hybrid progeny of crosses between certain strains. The syndrome includes high mutation rates, sterility, male recombination, distorted transmission ratios, chromosomal aberrations, non-disjunction and local increases in female recombination. Complex interstrain interactions are involved in the etiology of hybrid dysgenesis and environmental factors, such as temperature, also have a critical effect on its manifestation. The potential for hybrid dysgenesis is widespread in both natural and laboratory populations throughout the world. The objective of the proposed research is to investigate the etiology and mode of inheritance of one system of hybrid dysgenesis. Emphasis will be placed on determining the nature and mode of transmission of the two interacting components, i.e. the chromosomally linked "factors" and the cytoplasmic component. The possible transposability of the chromosomally linked "factors" will be investigated. The objective will be approached in a series of laboratory experiments using standard Drosophila techniques and previously tested strains.